Production of biofunctional recombinant human interleukin 1 receptor antagonist (rhIL1RN) from transgenic quail egg white

Study of the regulatory elements of the Ovalbumin gene promoter using CRISPR technology in chicken cells

BACKGROUND

Hormone-dependent promoters are very efficient in transgene expression. Plasmid-based reporter assays have identified regulatory sequences of the Ovalbumin promoter that are involved in response to estrogen and have shown that the deletion of the steroid-dependent regulatory element (SDRE) and negative regulatory element (NRE) leads to a steroid-independent expression of a reporter. However, the functional roles of these regulatory elements within the native genomic context of the Ovalbumin promoter have not been evaluated.

RESULTS

In this study, we show that the negative effects of the NRE element on the Ovalbumin gene can be counteracted by CRISPR interference. We also show that the CRISPR-mediated deletion of SDRE and NRE promoter elements in a non-oviduct cell can lead to the significant expression of the Ovalbumin gene. In addition, the targeted knock-in of a transgene reporter in the Ovalbumin coding region and its expression confirms that the truncated promoter of the Ovalbumin gene can be efficiently used for an estrogen-independent expression of a foreign gene.

CONCLUSIONS

The methodology applied in this paper allowed the study of promoter regulatory sequences in their native nuclear organization.

Genetically engineered birds; pre-CRISPR and CRISPR era

Generating biopharmaceuticals in genetically engineered bioreactors continues to reign supreme. Hence, genetically engineered birds have attracted considerable attention from the biopharmaceutical industry. Fairly recent genome engineering methods have made genome manipulation an easy and affordable task. In this review, we first provide a broad overview of the approaches and main impediments ahead of generating efficient and reliable genetically engineered birds, and various factors that affect the fate of a transgene. This section provides an essential background for the rest of the review, in which we discuss and compare different genome manipulation methods in the pre-CRISPR and CRISPR era in the field of avian genome engineering.

Improving germline transmission efficiency in chimeric chickens using a multi-stage injection approach

Although different strategies have been developed to generate transgenic poultry, low efficiency of germline transgene transmission has remained a challenge in poultry transgenesis. Herein, we developed an efficient germline transgenesis method using a lentiviral vector system in chickens through multiple injections of transgenes into embryos at different stages of development. The embryo chorioallantoic membrane (CAM) vasculature was successfully used as a novel route of gene transfer into germline tissues. Compared to the other routes of viral vector administration, the embryo’s bloodstream at Hamburger-Hamilton (HH) stages 14–15 achieved the highest rate of germline transmission (GT), 7.7%. Single injection of viral vectors into the CAM vasculature resulted in a GT efficiency of 2.7%, which was significantly higher than the 0.4% obtained by injection into embryos at the blastoderm stage. Double injection of viral vectors into the bloodstream at HH stages 14–15 and through CAM was the most efficient method for producing germline chimeras, giving a GT rate of 13.6%. The authors suggest that the new method described in this study could be efficiently used to produce transgenic poultry in virus-mediated gene transfer systems.

Isolation and characterization of cultured chicken oviduct epithelial cells and in vitro validation of constructed ovalbumin promoter in these cells

Objective

Transgenic hens hold a great promise to produce various valuable proteins. Through virus transduction into stage X embryo, the transgene expression under the control of constructed chicken ovalbumin promoters has been successfully achieved. However, a validation system that can evaluate differently developed ovalbumin promoters in in vitro, remains to be developed.

Methods

In the present study, chicken oviduct epithelial cells (cOECs) were isolated from oviduct tissue and shortly cultured with keratinocyte complete medium supplemented with chicken serum. The isolated cells were characterized with immunofluorescence, western blot, and flow cytometry using oviduct-specific marker. Chicken mutated ovalbumin promoter (Mut-4.4-kb-pOV) was validated in these cells using luciferase reporter analysis.

Results

The isolated cOECs revealed that the oviduct-specific marker, ovalbumin protein, was clearly detected by immunofluorescence, western blot, and flow cytometry analysis revealed that approximately 79.40% of the cells contained this protein. Also, luciferase reporter analysis showed that the constructed Mut-4.4-kb-pOV exhibited 7.1-fold (p<0.001) higher activity in the cOECs.

Conclusion

Collectively, these results demonstrate the efficient isolation and characterization of cOECs and validate the activity of the constructed ovalbumin promoter in the cultured cOECs. The in vitro validation of the recombinant promoter activity in cOECs can facilitate the production of efficient transgenic chickens for potential use as bioreactors.

Designing A Transgenic Chicken: Applying New Approaches toward A Promising Bioreactor

Specific developmental characteristics of the chicken make it an attractive model for the generation of transgenic organisms. Chicken possess a strong potential for recombinant protein production and can be used as a powerful bioreactor to produce pharmaceutical and nutritional proteins. Several transgenic chickens have been generated during the last two decades via viral and non-viral transfection. Culturing chicken primordial germ cells (PGCs) and their ability for germline transmission ushered in a new stage in this regard. With the advent of CRISPR/Cas9 system, a new phase of studies for manipulating genomes has begun. It is feasible to integrate a desired gene in a predetermined position of the genome using CRISPR/Cas9 system. In this review, we discuss the new approaches and technologies that can be applied to generate a transgenic chicken with regards to recombinant protein productions.

Secreting oviduct epithelial cells of Coturnix coturnix japonica (QOEC) and changes to their proteome after nonviral transfection

The quail oviduct (Coturnix c. japonica) is a natural candidate avian bioreactor, while the secretive quail oviduct epithelial cells (QOECs) are potential in vitro producers of recombinant proteins and vaccines. In view of the need for highly performing and transformable cell lines, QOEC may potentially act as an alternative bioreactor platform to the existing ones, for example, to the Chinese hamster ovary. The aim of this work was to characterize QOECs and their response to nucleofection with a nonviral plasmid DNA carrying the human interferon-α 2a gene (hIFNλ2a), in vitro. Primary QOEC cultures from laying quails (10-15 weeks old) were characterized by their proliferation rate, doubling time, and multilineage differentiation. Electroporation to cell nuclei (nucleofection) was used to deliver nonviral plasmid DNA containing a reporter GFP and hIFN under the ovalbumin promoter. The posttransfection analysis included polymerase chain reaction, Western blot analysis, and liquid chromatography coupled to tandem mass spectrometry. QOEC showed a typical epithelial characteristic in a primary 2D monolayer culture system and retained secretive potential up to the first passage. QOEC showed differentiation into osteoblastic lineage after stimulation. The nucleofection mean efficiency was low (2.3%). Differences of up to 10% in the proteomic profiles between nontransfected and transfected QOEC were found, the most important of these were related to the absence of keratins and cell-adhesion proteins in the transfected QOEC. Concluding, with the practical information provided here, QOEC have the potential to serve as an avian secreting cellular platform. QOEC may be further transformed to cell lineage to meet the requirement for a stable, electrocompetent, and transfectable model. The first proteomic comparison of QOEC delivered in this study showed, in the majority, a stable proteome of the nontransfected vs transfected QOEC.

Molecular signatures of epithelial oviduct cells of a laying hen (Gallus gallus domesticus) and quail (Coturnix japonica)

Background

In this work we have determined molecular signatures of oviduct epithelial and progenitor cells. We have proposed a panel of selected marker genes, which correspond with the phenotype of oviduct cells of a laying hen (Gallus gallus domesticus) and quail (Coturnix japonica). We demonstrated differences in characteristics of those cells, in tissue and in vitro, with respect to different anatomical and functional parts of the oviduct (infundibulum (INF), distal magnum (DM, and proximal magnum (PM)). The following gene expression signatures were studied: (1) oviduct markers (estrogen receptor 1, ovalbumin, and SPINK7 - ovomucoid), (2) epithelial markers (keratin 5, keratin 14, and occludin) and (3) stem-like/progenitor markers (CD44 glycoprotein, LGR5, Musashi-1, and sex determining region Y-box 9, Nanog homebox, OCT4/cPOUV gene encoding transcription factor POU5F3).

Results

In chicken, the expression of oviduct markers increased toward the proximal oviduct. Epithelial markers keratin14 and occludin were high in distal oviduct and decreased toward the proximal magnum. In quail oviduct tissue, the gene expression pattern of oviduct/epithelial markers was similar to chicken. The markers of progenitors/stemness in hen oviduct (Musashi-1 and CD44 glycoprotein) had the highest relative expression in the infundibulum and decreased toward the proximal magnum. In quail, we found significant expression of four progenitor markers (LGR5 gene, SRY sex determining region Y-box 9, OCT4/cPOUV gene, and CD44 glycoprotein) that were largely present in the distal oviduct. After in vitro culture of oviduct cells, the gene expression pattern has changed. High secretive potential of magnum-derived cells diminished by using decreased abundance of mRNA. On the other hand, chicken oviduct cells originating from the infundibulum gained ability to express OVM and OVAL. Epithelial character of the cells was maintained in vitro. Among progenitor markers, both hen and quail cells expressed high level of SOX9, LGR5 and Musashi-1.

Conclusion

Analysis of tissue material revealed gradual increase/decrease pattern in majority of the oviduct markers in both species. This pattern changed after the oviductal cells have been cultured in vitro. The results can provide molecular tools to validate the phenotype of in vitro biological models from reproductive tissue.

Electronic supplementary material

The online version of this article (10.1186/s12861-018-0168-2) contains supplementary material, which is available to authorized users.

The transgenic chicken derived anti-CD20 monoclonal antibodies exhibits greater anti-cancer therapeutic potential with enhanced Fc effector functions

Modern genetic techniques, enable the use of animal bioreactor systems for the production and functional enhancement of anti-cancer antibodies. Chicken is the most efficient animal bioreactor for the production of anti-cancer antibodies because of its relatively short generation time, plentiful reproductive capacity, and daily deposition in the egg white. Although several studies have focused on the production of anti-cancer antibodies in egg white, in-depth studies of the biological activity and physiological characteristics of transgenic chicken-derived anti-cancer antibodies have not been fully carried out. Here, we report the production of an anti-cancer monoclonal antibody against the CD20 protein from egg whites of transgenic hens, and validated the bio-functional activity of the protein in B-lymphoma and B-lymphoblast cells. Quantitative analysis showed that deposition of the chickenised CD20 monoclonal antibody (cCD20 mAb) from transgenic chickens increased in successive generations and with increasing transgene copy number. Ultra-performance liquid chromatography (UPLC) tandem mass spectrometry (LC/MS/MS) analysis showed that the cCD20 mAb exhibited 14 N-glycan patterns with high-mannose, afucosylation and terminal galactosylation. The cCD20 mAb did not exhibit significantly improved Fab-binding affinity, but showed markedly enhanced Fc-related functions, including complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) compared to commercial rituximab, a chimeric mAb against CD20. Our results suggest that the transgenic chicken bioreactor is an efficient system for producing anti-cancer therapeutic antibodies with enhanced Fc effector functions.

Generation of transgenic chickens by the non-viral, cell-based method: effectiveness of some elements of this strategy

Transgenic chickens have, in general, been produced by two different procedures. The first procedure is based on viral transfection systems. The second procedure, the non-viral method, is based on genetically modified embryonic cells transferred directly into the recipient embryo. In this review, we analyzed the effectiveness of important elements of the non-viral, cell-based strategy of transgenic chicken production. The main elements of this strategy are: isolation and cultivation of donor embryonic cells; transgene construction; cell transfection in vitro; and chimera production: injection of cells into recipient embryos, raising and identification of germline chimeras, mating germline chimeras, transgene inheritance, and transgene expression. In this overview, recent progress and important limitations in the development of transgenic chickens are presented.

Genome Modification Technologies and Their Applications in Avian Species

The rapid development of genome modification technology has provided many great benefits in diverse areas of research and industry. Genome modification technologies have also been actively used in a variety of research areas and fields of industry in avian species. Transgenic technologies such as lentiviral systems and piggyBac transposition have been used to produce transgenic birds for diverse purposes. In recent years, newly developed programmable genome editing tools such as transcription activator-like effector nuclease (TALEN) and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) have also been successfully adopted in avian systems with primordial germ cell (PGC)-mediated genome modification. These genome modification technologies are expected to be applied to practical uses beyond system development itself. The technologies could be used to enhance economic traits in poultry such as acquiring a disease resistance or producing functional proteins in eggs. Furthermore, novel avian models of human diseases or embryonic development could also be established for research purposes. In this review, we discuss diverse genome modification technologies used in avian species, and future applications of avian biotechnology.

Strategies to enable the adoption of animal biotechnology to sustainably improve global food safety and security

The ability to generate transgenic animals has existed for over 30 years, and from those early days many predicted that the technology would have beneficial applications in agriculture. Numerous transgenic agricultural animals now exist, however to date only one product from a transgenic animal has been approved for the food chain, due in part to cumbersome regulations. Recently, new techniques such as precision breeding have emerged, which enables the introduction of desired traits without the use of transgenes. The rapidly growing human population, environmental degradation, and concerns related to zoonotic and pandemic diseases have increased pressure on the animal agriculture sector to provide a safe, secure and sustainable food supply. There is a clear need to adopt transgenic technologies as well as new methods such as gene editing and precision breeding to meet these challenges and the rising demand for animal products. To achieve this goal, cooperation, education, and communication between multiple stakeholders-including scientists, industry, farmers, governments, trade organizations, NGOs and the public-is necessary. This report is the culmination of concepts first discussed at an OECD sponsored conference and aims to identify the main barriers to the adoption of animal biotechnology, tactics for navigating those barriers, strategies to improve public perception and trust, as well as industry engagement, and actions for governments and trade organizations including the OECD to harmonize regulations and trade agreements. Specifically, the report focuses on animal biotechnologies that are intended to improve breeding and genetics and currently are not routinely used in commercial animal agriculture. We put forward recommendations on how scientists, regulators, and trade organizations can work together to ensure that the potential benefits of animal biotechnology can be realized to meet the future needs of agriculture to feed the world.

Advances in genetic engineering of the avian genome: "Realising the promise"

This review provides an historic perspective of the key steps from those reported at the 1st Transgenic Animal Research Conference in 1997 through to the very latest developments in avian transgenesis. Eighteen years later, on the occasion of the 10th conference in this series, we have seen breakthrough advances in the use of viral vectors and transposons to transform the germline via the direct manipulation of the chicken embryo, through to the establishment of PGC cultures allowing in vitro modification, expansion into populations to analyse the genetic modifications and then injection of these cells into embryos to create germline chimeras. We have now reached an unprecedented time in the history of chicken transgenic research where we have the technology to introduce precise, targeted modifications into the chicken genome, ranging from; new transgenes that provide improved phenotypes such as increased resilience to economically important diseases; the targeted disruption of immunoglobulin genes and replacement with human sequences to generate transgenic chickens that express "humanised" antibodies for biopharming; and the deletion of specific nucleotides to generate targeted gene knockout chickens for functional genomics. The impact of these advances is set to be realised through applications in chickens, and other bird species as models in scientific research, for novel biotechnology and to protect and improve agricultural productivity.

Oviduct-specific expression of human neutrophil defensin 4 in lentivirally generated transgenic chickens

The expression of oviduct-specific recombinant proteins in transgenic chickens is a promising technology for the production of therapeutic biologics in eggs. In this study, we constructed a lentiviral vector encoding an expression cassette for human neutrophil defensin 4 (HNP4), a compound that displays high activity against Escherichia coli, and produced transgenic chickens that expressed the recombinant HNP4 protein in egg whites. After the antimicrobial activity of the recombinant HNP4 protein was tested at the cellular level, a 2.8-kb ovalbumin promoter was used to drive HNP4 expression specifically in oviduct tissues. From 669 injected eggs, 218 chickens were successfully hatched. Ten G₀ roosters, with semens identified as positive for the transgene, were mated with wild-type hens to generate G₁ chickens. From 1,274 total offspring, fifteen G₁ transgenic chickens were positive for the transgene, which was confirmed by PCR and Southern blotting. The results of the Southern blotting and genome walking indicated that a single copy of the HNP4 gene was integrated into chromosomes 1, 2, 3, 4, 6 and 24 of the chickens. As expected, HNP4 expression was restricted to the oviduct tissues, and the levels of both transcriptional and translational HNP4 expression varied greatly in transgenic chickens with different transgene insertion sites. The amount of HNP4 protein expressed in the eggs of G₁ and G₂ heterozygous transgenic chickens ranged from 1.65 μg/ml to 10.18 μg/ml. These results indicated that the production of transgenic chickens that expressed HNP4 protein in egg whites was successful.

Human extracellular superoxide dismutase (EC-SOD) expression in transgenic chicken

Extracellular superoxide dismutase (EC-SOD) is a metalloprotein and functions as an antioxidant enzyme. In this study, we used lentiviral vectors to generate transgenic chickens that express the human EC-SOD gene. The recombinant lentiviruses were injected into the subgerminal cavity of freshly laid eggs. Subsequently, the embryos were incubated to hatch using phases II and III of the surrogate shell ex vivo culture system. Of 158 injected embryos, 16 chicks (G0) hatched and were screened for the hEC-SOD by PCR. Only 1 chick was identified as a transgenic bird containing the transgene in its germline. This founder (G0) bird was mated with wild-type hens to produce transgenic progeny, and 2 transgenic chicks (G1) were produced. In the generated transgenic hens (G2), the hEC-SOD protein was expressed in the egg white and showed antioxidant activity. These results highlight the potential of the chicken for production of biologically active proteins in egg white. [BMB Reports 2013; 46(8): 404-409]

Transgenesis and imaging in birds, and available transgenic reporter lines

Avian embryos are important model organism to study higher vertebrate development. Easy accessibility to developing avian embryos enables a variety of experimental applications to understand specific functions of molecules, tissue-tissue interactions, and cell lineages. The whole-mount ex ovo culture technique for avian embryos permits time-lapse imaging analysis for a better understanding of cell behaviors underlying tissue morphogenesis in physiological conditions. To study mechanisms of blood vessel formation and remodeling in developing embryos by using a time-lapse imaging approach, a transgenic quail model, Tg(tie1:H2B-eYFP), was generated. From a cell behavior perspective, Tg(tie1:H2B-eYFP) quail embryos are a suitable model to shed light on how the structure and pattern of blood vessels are established in higher vertebrates. In this manuscript, we give an overview on the biological and technological background of the transgenic quail model and describe procedures for the ex ovo culture of quail embryos and time-lapse imaging analysis.

Genetic modification of chicken germ cells

Over the past two decades numerous reports have demonstrated that the genetic modification of poultry genomes has great potential for improving poultry production; moreover, it may be used as a powerful tool for the production of industrial proteins. To date, transgenic techniques have been established for generating transgenic birds that express recombinant human proteins in hen eggs, as well as tissue-specific genes as an animal model. The production of transgenic birds is a promising approach that could have practical applications in agriculture and biopharmacology, in addition to advancing our understanding of avian biology. Finally, germ cell-mediated transgenesis could provide a more efficient strategy for creating gene-targeted insertions and deletions in avian species.

Structural and histological characterization of oviductal magnum and lectin-binding patterns in Gallus domesticus

BACKGROUND

Although chicken oviduct is a useful model and target tissue for reproductive biology and transgenesis, little is known because of the highly specific hormonal regulation and the lack of fundamental researches, including lectin-binding activities and glycobiology. Because lectin is attached to secreted glycoproteins, we hypothesized that lectin could be bound to secretory egg-white proteins, and played a crucial role in the generation of egg-white protein in the oviduct. Hence, the purpose of this study was to investigate the structural, histological and lectin-binding characteristics of the chicken oviductal magnum from juvenile and adult hens.

METHODS

The oviductal magnums from juvenile and adult hens were prepared for ultrastructural analysis, qRT-PCR and immunostaining. Immunohistochemistry of anti-ovalbumin, anti-ESR1 and anti-PGR, and mRNA expression of egg-white genes and steroid hormone receptor genes were evaluated. Lectin histochemical staining was also conducted in juvenile and adult oviductal magnum tissues.

RESULTS

The ultrastructural analysis showed that ciliated cells were rarely developed on luminal surface in juvenile magnum, but not tubular gland cells. In adult magnum, two types of epithelium and three types of tubular gland cells were observed. qRT-PCR analysis showed that egg-white genes were highly expressed in adult oviduct compared with the juvenile. However, mRNA expressions of ESR1 and PGR were considerably higher in juvenile oviduct than adult (P < 0.05). The immunohistochemical analysis showed that anti-ovalbumin antibody was detected in adult oviduct not in juvenile, unlikely anti-ESR1 and anti-PGR antibodies that were stained in both oviducts. In histological analysis, Toluidine blue was stained in juvenile and adult oviductal epithelia, and adult tubular glands located in the outer layer of oviductal magnum. In contrast, PAS was positive only in adult oviductal tubular gland. Lectins were selectively bound to oviductal epithelium, stroma, and tubular gland cells. Particularly, lectin-ConA and WGA were bound to electron-dense secretory granules in tubular gland.

CONCLUSIONS

The observation of ultrastructural analysis, mRNA expression, immunohistochemistry and lectin staining showed structural and physiological characterization of juvenile and adult oviductal magnum. Consequently, oviduct study could be helped to in vitro culture of chicken oviductal cells, to develop epithelial or tubular gland cell-specific markers, and to understand female reproductive biology and endocrinology.

Oviduct-specific expression of tissue plasminogen activator in laying hens

Egg-laying hens are important candidate bioreactors for pharmaceutical protein production because of the amenability of their eggs for protein expression. In this study, we constructed an oviduct-specific vector containing tissue plasminogen activator (tPA) protein and green fluorescent protein (pL-2.8OVtPAGFP) and assessed its expression in vitro and in vivo. Oviduct epithelial and 3T3 cells were cultured and transfected with pL-2.8OVtPAGFP and pEGP-N1 (control vector), respectively. The pL-2.8OVtPAGFP vector was administered to laying hens via a wing vein and their eggs and tissues were examined for tPA expression. The oviduct-specific vector pL-2.8OVtPAGFP was expressed only in oviduct epithelial cells whereas pEGP-N1 was detected in oviduct epithelial and 3T3 cells. Western blotting detected a 89 kDa band corresponding to tPA in egg white and oviduct epithelial cells, thus confirming expression of the protein. The amount of tPAGFP in eggs ranged 9 to 41 ng/mL on the third day after vector injection. The tPA expressed in egg white and oviduct epithelial cells showed fibrinolytic activity, indicating that the protein was expressed in active form. GFP was observed only in oviducts, with no detection in heart, muscle, liver and intestine. This is the first study to report the expression of tPA in egg white and oviduct epithelial cells using an oviduct-specific vector.